Towing Services Glossary - King's Towing Tacoma, Washington

Some people are determined to tow their own vehicles. With the many different kinds of drives suspension of today's cars and truck we do not recommend it, but here is a glossary of towing terms to help you make the right decision about towing if you have to do it yourself.

Ball mount - The part of the hitch system that
supports the hitch ball and connects it to the trailer coupler. Ball
mounts are available in load-carrying and weight-distributing
configurations. An adjustable ball mount allows a hitch ball to be
raised, lowered and tilted in small increments to allow fine tuning
of the spring bar setup and to compensate for tow vehicle
"squat," which occurs after the trailer coupler is lowered
onto the ball.

Base Curb Weight (BCW) - BCW is the weight of a
vehicle with standard equipment and a full tank of fuel. It does not
include passengers, cargo or optional equipment.

BCW see above

Brake controller - A control unit mounted
inside your RV that allows electric trailer brakes to become
activated in harmony with the braking of the tow vehicle. This device
can be used to adjust trailer brake intensity, or to manually
activate the trailer brakes.

Breakawayswitch - A safety device that
activates the trailer brakes in the event the trailer becomes
accidentally disconnected from the hitch while traveling.

Cargo Weight (CW) - The cargo weight includes
all the weight added to the Base
Curb Weight (BCW), including the passengers, the cargo
and any optional equipment. When towing, the trailer tongue weight
also has to be included in the cargo weight.

Class A motorhome - An RV with the living
accommodations built on or as an integral part of a self-propelled
motor vehicle. Models range from 24 to 40 feet long.

Class B motorhome - Also known as a camping van
conversion. These RVs are built within the dimensions of a van, but
with a raised roof to provide additional headroom. Basic living
accommodations inside are ideal for short vacations or weekend trips.
Models usually range from 16 to 21 feet.

Class C motorhome - An RV with the living
accommodations built on a cutaway van chassis. A full-size bed in the
"cabover" section allows for ample seating, galley and
bathroom facilities in the coach. Also called a
"mini-motorhome" or "mini." Lengths range from
approximately 16 to 32 feet.

Coupler - The part of a trailer A-frame that
attaches to the hitch ball.

Curb Weight (CW) - Also known as Net Weight.
The weight of the RV as it is sitting on the lot, without the
personal load you will be adding.

Dinghy - A vehicle towed behind a motorhome,
sometimes with two wheels on a special trailer called a tow dolly,
but often with all four wheels on the ground.

Dry Weight (DW) - The weight of the RV without
adding fuel, water, propane, supplies and passengers. The
manufacturers UVW will not include any dealer-installed options. Also
known as Unloaded Vehicle Weight.

Dually - A pickup truck, or light-duty tow
vehicle, with four tires on one rear axle.

Dullies - Dual Tires.

Engine oil cooler - A heat exchanger, similar
to a small radiator, through which engine oil passes and is cooled by airflow.

Fifth-wheel trailers - Fifth-wheel trailers are
trailers designed to be coupled to a special hitch that is mounted
over the rear axle in the bed of a pickup truck. These trailers can
have one, two or three axles and are the largest type of trailer
built. Because of their special hitch requirements, fifth-wheel
trailers can only be towed by trucks or specialized vehicles prepared
for fifth-wheel trailer compatibility.

Frame-mount hitch - Class II and higher hitches
are designed to be bolted to the vehicle frame or cross members. This
type of hitch may have a permanent ball mount, or may have a
square-tube receiver into which a removable hitch bar or shank is installed.

Gross Axle Weight (GAW) - The total weight
supported by each vehicle's axle (front or rear). To obtain this
number, you have to weigh the vehicle and the trailer on a scale.

Gross Axle Weight Rating (GAWR) - The
manufacturer's rating for the maximum allowable weight that an axle
is designed to carry. GAWR applies to tow vehicle, trailer,
fifth-wheel and motorhome axles.

Gross Combined Weight (GCW) - The actual weight
of a vehicle and trailer combined. To obtain this number, you have to
weigh the vehicle and the trailer together on a scale.

Gross Combination Weight Rating (GCWR) - The
maximum allowable weight of the combination of tow vehicle and
trailer/fifth-wheel, or motorhome and dinghy. It includes the weight
of the vehicle, trailer/fifth-wheel (or dinghy), cargo, passengers
and a full load of fluids (fresh water, propane, fuel, etc.).

Gross Trailer Weight (GTW) - Gross trailer
weight is the weight of the trailer fully loaded in its actual towing
condition. GTW is measured by placing the fully loaded trailer on a
vehicle scale. The entire weight of the trailer should be supported
on the scale.

Gross Vehicle Weight Rating (GVWR) - The total
allowable weight of a vehicle, including passengers, cargo, fluids
and hitch weight.

Hitch ratings - Hitches are rated by the
manufacturers according to the maximum amount of weight they are
engineered to handle. Class I travel trailer hitches are rated for
towing as much as 2,000 pounds. Class II units are for loads up to
3,500 pounds. Class III has a rating of 7,500 pounds, and Class IV is
for loads of up to 10,000 pounds. Class V hitches are designed for
towing loads up to 14,000 pounds. These ratings may vary depending on
the manufacturer. Fifth-wheel ratings range to 25,000 pounds. The
weight rating refers to the total weight of the trailer/fifth-wheel,
with freshwater tank full, propane tanks full, all supplies on-board
and ready to travel.

Hitch weight - The amount of weight imposed on
the hitch when the trailer is coupled. Also referred to as
"tongue weight". Hitch weight for a travel trailer can be
10-15 percent of overall weight; fifth-wheel hitch weight is usually
18-20 percent of the overall weight.

Light Weight RV - RVs that are designed to be
easily towed behind most Minivans, light-duty trucks and cars! The
most common being a pop-up trailer.

Net Carrying Capacity (NCC) - The amount of
cargo, passenger and fluid weight that can be added to an RV without
exceeding its GVWR.
The NCC label in an RV may not include the weight of dealer
installed or factory installed options already on the vehicle.
Subtract UVW from the GVWR
and the result is what can be added to the factory weight.

Receiver - The portion of a hitch that permits
a hitch bar or shank to be inserted. The receiver may be either
11/2-, 15/8- or 2-inch square; the smallest being termed a mini-hitch.

Safety chains - A set of chains that are
attached to the trailer A-frame and connected to the tow vehicle
while towing. Safety chains are intended to keep the trailer attached
to the tow vehicle in the event of hitch failure, preventing the
trailer from complete separation. They should be installed using an
X-pattern (criss-crossed) so the coupler is held off the road in the
event of a separation.

Shank - Also called a hitch bar or stinger. A
shank is a removable portion of the hitch system that carries the
ball or adjustable ball mount, and slides into the receiver.

Spring bar - Component parts of a
weight-distributing hitch system. The spring bars are installed and
tensioned in such a manner as to distribute a portion of the
trailer's hitch weight to the front axle of the tow vehicle and to
the axles of the trailer.

Sway - Refers to the "fish-tailing"
action of a trailer caused by external forces that set the trailer's
mass into a lateral (side-to-side) motion. The trailer's wheels serve
as the axis or pivot point. . Also known as "yaw".

Sway control - Devices designed to damp the
swaying (fish-tailing) action of a trailer, either through a friction
system or a "cam action" system that slows and absorbs the
pivotal articulating action between tow vehicle and trailer. The most
common device in use is a "sway bar".

Tail swing - All motorhomes built on chassis
with short wheelbases and long overhangs behind the rear axle are
susceptible to "tail swing" when turning sharply. As the
motorhome moves in reverse or turns a corner, its extreme rear can
move horizontally and strike objects nearby (typically road signs and
walls). Drivers need to be aware of the amount of "tail
swing" in order to prevent accidents.

Tongue Weight (TW) - The amount of weight imposed on
the hitch when the trailer is coupled. Also referred to as "hitch
weight". Tongue weight for a travel trailer can be 10-15
percent of overall weight; fifth-wheel hitch weight is usually 18-20
percent of the overall weight.

Tow bar - A device used for connecting a dinghy
vehicle to the motorhome when it's towed with all four wheels on the ground.

Tow rope or tow strap - A multi-fiber rope or strap connecting two vehicles for one to pull the other.

Tow rating - The manufacturer's rating of the
maximum weight limit that can safely be towed by a particular
vehicle. Tow ratings are related to overall trailer weight, not
trailer size, in most cases. However, some tow ratings impose limits
as to frontal area of the trailer and overall length. Tow ratings are
determined by the vehicle manufacturer according to several criteria,
including engine size, transmission, axle ratio, brakes, chassis,
cooling systems and other special equipment.

Trailer brakes - Brakes that are built into the
trailer axle systems and are activated either by electric impulse or
by a surge mechanism. The overwhelming majority of RVs utilize
electric trailer brakes that are actuated when the tow vehicle's
brakes are operated, or when a brake controller is manually
activated. Surge brakes utilize a mechanism positioned at the coupler
that detects when the tow vehicle is slowing or stopping and
activates the trailer brakes via a hydraulic system.

Transmission cooler - A heat exchanger similar
to a small radiator through which automatic transmission fluid passes
and is cooled by airflow.

Travel trailer - Also referred to as
"conventional trailers" these types of trailers have an
A-frame and coupler and are attached to a ball mount on the tow
vehicle. Travel trailers are available with one, two or three axles.

Umbilical cord - The wiring harness that
connects the tow vehicle to the trailer, supplying electricity to the
trailer's clearance and brake lights, electric brakes and a 12-volt
DC power line (to charge the trailer's batteries).

Unloaded Vehicle Weight (UVW) - The weight of
the RV without adding fuel, water, propane, supplies and passengers.
The manufacturers UVW will not include any dealer-installed options.
Also known as Dry Weight.

Weight carrying hitch - Also known as a
"dead-weight" hitch, this category includes any system that
accepts the entire hitch weight of the trailer. In the strictest
sense, even a weight-distributing hitch can act as a load-carrying
hitch if the spring bars are not installed and placed under tension.

Weight distributing hitch - Also known as an
"equalizing" hitch, this category includes hitch systems
that utilize spring bars that can be placed under tension to
distribute a portion of the trailer's hitch weight to the tow
vehicle's front axle and the trailer's axles.

Wet weight - The weight of the vehicle with the
fuel, freshwater and propane tanks full.

Wheelbase - The distance between the center
lines of the primary axles of a vehicle. If a motorhome includes a
"tag" axle, the distance is measured from the front axle to
the center point between the drive and "tag" axle.

Yaw - Refers to the "fish-tailing"
action of a trailer caused by external forces that set the trailer's
mass into a lateral (side-to-side) motion. The trailer's wheels serve
as the axis or pivot point. Also known as "sway".

Full Towing Services in Tacoma and South Puget Sound

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